hibernate/hibernate-orm · error · MappingException

${className} does not implement 'Generator'

Error message

${className} does not implement 'Generator'

What it means

Error "${className} does not implement 'Generator'" thrown in hibernate/hibernate-orm.

Source

Thrown at hibernate-core/src/main/java/org/hibernate/boot/model/internal/GeneratorStrategies.java:111

				return ForeignGenerator.class;
			case "uuid":
			case "uuid.hex":
				return UUIDHexGenerator.class;
			case "uuid2":
				return UUIDGenerator.class;
			case "select":
				return SelectGenerator.class;
			case "guid":
				return GUIDGenerator.class;
		}
		final Class<? extends Generator> clazz =
				idValue.getBuildingContext().getBootstrapContext()
						.getClassLoaderService()
						.classForName( strategy );
		if ( !Generator.class.isAssignableFrom( clazz ) ) {
			// in principle, this shouldn't happen, since @GenericGenerator
			// constrains the type to subtypes of Generator
			throw new MappingException( clazz.getName() + " does not implement 'Generator'" );
		}
		return clazz;
	}

	public static Class<? extends Generator> mapLegacyNamedGenerator(String strategy, Dialect dialect) {
		if ( "native".equals(strategy) ) {
			strategy = dialect.getNativeIdentifierGeneratorStrategy();
		}
		switch (strategy) {
			case "assigned":
				return org.hibernate.id.Assigned.class;
			case "enhanced-sequence":
			case "sequence":
				return SequenceStyleGenerator.class;
			case "enhanced-table":
			case "table":
				return org.hibernate.id.enhanced.TableGenerator.class;
			case "identity":

View on GitHub (pinned to fad1729dce)

Solutions

1. Make the referenced class implement the Generator interface.

When it happens

Trigger: An identifier/value generator declaration is inconsistent with the referenced generator or the annotated element.

Common situations: @GeneratedValue pointing at a generator of the wrong kind (SEQUENCE vs TABLE), a missing named generator, too many generator annotations, or an unsupported generation strategy for @CollectionId.

AI-assisted analysis of hibernate/hibernate-orm@fad1729dce (2026-08-22). Data as JSON: /api/errors/af68b8f2f624fee1. Report an issue: GitHub.